LMB-1 is an immunotoxin made of MAb B3 chemically coupled to PE38, a recombinant truncated form of Pseudomonas exotoxin lacking the cell binding domain. B3 is a murine mAb, IgG1k, that recognizes a carbohydrate antigen in the LewisY family, present on the surface of many human solid tumors. LMB-1 has been shown to have excellent anti-tumor activity in vitro and in nude mice bearing tumors that express the B3 antigen. A phase I study to access the toxicity, the pharmacokinetics the immunogenicity, and the anti-tumor activity of LMB-1 is ongoing at the Medicine Branch, NCI. Patients with advanced solid tumor who have failed standard therapy are all potentially eligible. These include patients with colon, esophagus, gastric, breast, lung, ovarian or transitional cell carcinoma of the bladder. The patient's tumor tissue must express the B3 antigen on more than 30% of the cells and the patient must not have neutralizing antibodies to LMB-1 prior to therapy. To date, 22 patients with breast and gastrointestinal cancer have been entered at doses ranging from l0micrograms/kg/d to l00micrograms/kg/d given as 30 min bolus on days l, 3, and 5. The major side effect is Capillary Leak Syndrome. Almost all patients developed antibodies against LMB-1 after the first cycle. Anti- tumor activity was observed in 2 patients.